1. Field of the Invention
The present invention relates to a hybrid compressor apparatus, preferably, applicable to a refrigeration cycle system installed in a vehicle having an idle stop mechanism in which an engine stops with temporary stop of the vehicle during its traveling.
2. Description of the Prior Art
Recently, a vehicle incorporating an idle stop mechanism has been put on a market in view of saving fuel consumption. In this vehicle, a compressor for a refrigeration cycle system, driven by an engine, is obliged to stop, when the engine stops with temporary stop of the vehicle during its traveling. Accordingly, the refrigeration cycle system does not work as a cooler during a period when the engine stops.
U.S. Pat. No. 6,375,436 discloses a hybrid compressor apparatus in which the above problem is solved. According to this hybrid compressor apparatus, a pulley to which rotating force of the engine is communicated is linked via an electromagnetic clutch to a compressor and, further, a motor is linked to a rotating shaft of the compressor on a side opposite to the pulley. With this construction, when the engine stops, the electromagnetic clutch is turned off and the motor drives the compressor. Accordingly, the refrigeration cycle system is always operative for performing cooling function irrespective of whether the engine stops or not.
However, in the hybrid compressor apparatus mentioned above, the motor for driving the compressor is used only when the engine stops and is not used as a drive unit during any vehicle traveling conditions.
Capacity of the compressor is decided to meet a maximum thermal load required in the refrigeration cycle system. The thermal load shows a maximum value, typically, at a rapid cooling time (at a cool down time) just after the engine starts in summer season. Accordingly, the capacity of the compressor has to be relatively large to meet the maximum thermal load requirement. In a case that the compressor is driven only by the engine whose operation depends on the vehicle traveling conditions, the larger capacity of the compressor results in a larger body size of the compressor.